This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
A variety of diagnostic, laboratory, and other systems (e.g., radiation-based treatment systems) may utilize X-ray tubes as a source of radiation. Typically, the X-ray tube includes a cathode and an anode. An emitter within the cathode may emit a stream of electrons. The anode may include a target that is impacted by the stream of electrons. As a result of this impact, the target may emit radiation. A large portion of the energy deposited into the target by the electron beam produces heat, with another portion of the energy resulting in the production of X-ray radiation. Of the X-ray radiation that is emitted, two types may result: (1) Bremsstrahlung radiation, which is typically emitted toward a subject of interest for treatment or imaging, and (2) characteristic radiation, which is a result of fluorescence from the target atoms and is typically emitted isotropically.
In imaging systems, for example, X-ray tubes are used in projection X-ray systems, fluoroscopy systems, tomosynthesis systems, mammography systems, and computed tomography (CT) systems as a source of X-ray radiation. In these implementations, images are produced by variations in contrast resulting from the different attenuation of X-rays by various materials in the sample or subject. Other techniques, such as diffraction-based phase contrast imaging, may produce images by variations in contrast resulting from differences in the refractive indices of different materials in the subject. Thus, diffraction-based imaging may be used to distinguish between materials having similar X-ray attenuation. While medical X-ray imaging systems typically utilize conventional X-ray tubes, some diffraction-based medical techniques use X-ray sources with higher flux than laboratory-based sources are typically able to provide.
For example, as noted above, during the operation of an X-ray source, the electron beam impacts and deposits energy into the source target, resulting in heat and X-ray radiation. The X-ray flux is, therefore, highly dependent upon the amount of energy that can be deposited into the source target by the electron beam within a given period of time. However, the relatively large amount of heat produced during operation, if not mitigated, can damage the X-ray source (e.g., melt the target). Accordingly, conventional X-ray sources are typically cooled by either rotating or actively cooling the target. However, when rotation is the means of avoiding overheating, the amount of deposited heat is limited by the rotation speed (RPM) and the life of the supporting bearings, this limits the amount of deposited heat and X-ray flux. This also increases the overall volume, and weight of the X-ray source systems. When the target is actively cooled, such cooling generally occurs far from the electron beam impact area, which in turn significantly limits the electron beam power that can be applied to the target. In both situations, the restricted heat removal ability of the cooling methods markedly lowers the overall flux of X-rays that are generated by the X-ray tube.